Problem: $ { \left[\begin{array}{rr}{2} & {2} \\ {3} & {4}\end{array}\right]-\left[\begin{array}{rr}{1} & {1} \\ {2} & {-1}\end{array}\right] = {?} } $
Explanation: To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{rr}{2}-{1} & {2}-{1} \\ {3}-{2} & {4}-{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{1} & {1} \\ {1} & {5}\end{array}\right]}$